This application claims priority to Japanese Patent Application No. P2000-211117 filed on Jul. 12, 2000 in Japan. The contents of the aforementioned application are hereby incorporated by reference.
1. Field of the Invention
This invention relates to a shift control apparatus of an automatic transmission for a vehicle.
2. Description of the Related Art
For a shift control apparatus of an automatic transmission for a vehicle, hitherto, various arts have been proposed; for example, in an art described in JP-B-3-16545, a temporary rise in the engine speed during shifting is captured and the preparation time for a clutch on the engagement side (frictional engagement element) and engagement hydraulic pressure are corrected. In an art described in JP-A-11-82704, low-pressure standby time (preparation time) is corrected as the invalid stroke feeding time of a clutch is changed, whereby the servo start control time is controlled constant.
By the way, in an automatic transmission, generally a hydraulic clutch (frictional engagement element) is used and the clutch clearance differs depending on not only manufacturing variations, but also secular change. This also applies to the I-P characteristic (energization-hydraulic pressure) of an electromagnetic solenoid for driving a clutch.
For example, shortage of the preparation time or engagement hydraulic pressure is possible as a factor of raising the engine rotation speed. It is difficult to determine whether it is actually caused by a shift of the clutch clearance or the I-P characteristic of the electromagnetic solenoid from the setup value or caused by an error of hydraulic pressure control. Determining the cause requires a large number of data pieces during shifting and is substantially impossible.
It is therefore an object of the invention to provide a shift control apparatus of an automatic transmission for a vehicle for effectively canceling raising of the engine rotation speed regardless of the cause of the raising the engine rotation speed by making a learn correction to hydraulic pressure control and making the learn correction based on a predetermined correction ratio.
To the end, according to a first aspect of the invention, there is provided a shift control apparatus of an automatic transmission for a vehicle, comprising a plurality of frictional engagement elements driven by electromagnetic solenoids wherein hydraulic pressure is applied to the frictional engagement element on the engagement side and hydraulic pressure is discharged from the frictional engagement element on the release side for shifting output of an internal combustion engine, the shift control apparatus comprising hydraulic pressure control means for, at predetermined shifting time, outputting preparation hydraulic pressure based on preparation hydraulic pressure previously stored in the frictional engagement element on the engagement side and previously stored preparation time and next outputting engagement hydraulic pressure based on previously stored engagement hydraulic pressure characteristic relative to the target hydraulic pressure, raising occurrence detection means for determining whether or not raising the rotation speed occurs in the internal combustion engine by the time an inertia phase starts, and learn correction means for making a hydraulic pressure learn correction to the preparation hydraulic pressure and the engagement hydraulic pressure and a time learn correction to the preparation time at the next predetermined shifting time when the raising occurrence detection means detects raising the rotation speed of the internal combustion engine, wherein the learn correction means makes the hydraulic pressure learn correction and the time learn correction based on a predetermined correction ratio.
The learn correction means is provided for making a hydraulic pressure learn correction to the preparation hydraulic pressure and the engagement hydraulic pressure and more particularly a hydraulic pressure learn correction to the hydraulic pressure height and a time learn correction to the preparation time and more particularly a time learn correction to the duration of the preparation time at the next predetermined shifting time when raising of the rotation speed of the internal combustion engine is detected, and the learn correction means makes the hydraulic pressure learn correction and the time learn correction based on the predetermined correction ratio, so that the learn progress state can be reliably converged toward the target level and therefore raising of the rotation speed of the internal combustion engine can be canceled effectively.
In a second aspect of the invention, the predetermined correction ratio is a predetermined correction ratio relative to the energization-hydraulic pressure characteristic of the electromagnetic solenoid and clearance of the frictional engagement element.
Since the predetermined correction ratio is a predetermined correction ratio relative to the energization-hydraulic pressure characteristic of the electromagnetic solenoid and clearance of the frictional engagement element, the initial manufacturing variations and secular change in clearance of the frictional engagement element (clutch) can be corrected based on the duration of the preparation time and shift of a control signal and the actual supplied hydraulic pressure can be corrected based on the height of the hydraulic pressure; the learn progress state can be reliably converged toward the target level and therefore raising of the rotation speed of the internal combustion engine can be canceled effectively.